Gas turbines and their principles of operation are generally known. In relation to this, FIG. 4 shows a gas turbine 1 which has a compressor 5, a combustion chamber 6 and a turbine unit 11 installed along a rotor 3 rotatably mounted around a rotational axis 2. In the compressor 5 and also in the turbine unit 11 stator blades 12,35 are fastened on the casing and rotor blades 15,37 are fastened on the rotor 3, each with the forming of blade rings 17,19,36,38. A stator blade ring 19,36 forms with the rotor blade ring 17,38 a compressor stage 21 or a turbine stage 34 respectively, wherein a plurality of stages are connected one behind the other. The rotor blades 15 of a ring 17,38 are fastened on the rotor 3 by means of an annular, centrally perforated disk 26,39. Extending through the central opening in the axial direction is a central tension bolt 7 which clamps together the turbine disks 39 and compressor disks 26. In addition, a hollow shaft 13 is installed to bridge the distance originating from the combustion chamber 6, between the compressor 5 and turbine unit 11, between the compressor disk 26 of the last compressor stage 21 and the turbine disk 39 of the first turbine stage 34.
During the running of the gas turbine 1 the compressor 5 draws in ambient air and compresses this. The compressed air is mixed with a fuel and fed to the combustion chamber 6 in which the mixture is combusted into a hot working medium M. The latter flows from out the combustion chamber 6 into the turbine unit 11 and by means of the rotor blades 15 drives the rotor 3 of the gas turbine 1 which drives the compressor 5 and a working machine such as a generator.
The torque acting on the rotor blades of the turbine unit and produced by the working medium is transmitted to the generator as useful energy and to the compressor as driving energy for the compressing of the ambient air. Consequently, the hollow shaft has to transmit the driving energy required for the compressing of the ambient air in the compressor from the turbine disk of the first turbine stage to the compressor disk of the last compressor stage.
This arrangement inside the turbine causes the hollow shaft to be subjected to especially high mechanical loads. These loads can lead to creep deformations and to defects which then lead to a reduction of the service life of the rotor.
In addition, lying radially adjacent to the hollow shaft is the combustion chamber of the gas turbine which can unacceptably heat this axial region of the rotor during operation. Therefore, thermal loads also can occur which can diminish the strength as also the rigidity of the hollow shaft so that the occurring mechanical load induces a premature fatigue of the material of the hollow shaft.
Moreover, from GB 836,920 a rotor for a compressor is known which is formed from a plurality of abutting, clamped compressor disks. The compressor disks have a central opening which forms a hollow shaft.
Furthermore, GB 661,078 shows a hollow shaft for a gas turbine rotor which is formed from two abutting tubular pieces radially inside the combustion chamber.